Sa. Picaud et al., GLUTAMATE-GATED CHLORIDE CHANNEL WITH GLUTAMATE-TRANSPORTER-LIKE PROPERTIES IN CONE PHOTORECEPTORS OF THE TIGER SALAMANDER, Journal of neurophysiology, 74(4), 1995, pp. 1760-1771
1. Using the patch-clamp technique, we investigated whether the glutam
ate-elicited current in mechanically isolated cone photoreceptors from
the salamander retina is generated by a Cl- channel or a glutamate tr
ansporter. 2. The current reversed near the equilibrium potential for
Cl-, was decreased by three Cl- channel blockers, 5-nitro-2-(3-phenyl-
propylamino) benzoic acid, 4,4'-diisothiocyanostilbene-2,2'-disulfonat
e, and diphenylamine 2,2'-dicarboxylic acid, and was eliminated when g
luconate was substituted for both internal and external Cl-, features
consistent with the current being mediated by a Cl- channel. 3. The si
ngle-channel conductance of the Cl- channel was estimated by noise ana
lysis of the glutamate-elicited current fluctuations to be 0.7 pS with
an open time of 2 ms. 4. The magnitude of the current was dependent o
n both internal and external Na+ and K+, features consistent with the
current being related to the activation of a glutamate transporter. Ye
t changes in their concentrations did not affect the reversal potentia
l of the current. 5. Taken together with earlier reports on this curre
nt showing a that it has a glutamate-transporter-like pharmacology, ou
r results suggest that the glutamate-elicited current is carried by a
Cl- channel but gated by a glutamate receptor whose pharmacology and i
onic requirement resemble those previously described for glutamate tra
nsporters.